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Tuesday, May 01, 2012

Comments at beginning of line?

code; // we have comments at the end of a line
code /* and comments anywhere on a line, like in the middle */ code;
/* where "anywhere" can be at the beginning: */ code;

but it occurs to me that I often want comments at the beginning of a line, e.g.

     /* arg1= */ 111,
     /* arg2= */ 222,

and although /*...*/ can accomplish this, they are visually heavyweight.

I wonder if, in a hypothetical new language, we could have comments from the beginning of a line?

Now, ":" would be the most natural comment delimiter for this - if it were not already used for so much else:

     arg1:  111,
     arg2:  222,

Note that I have distinguished comments in a special color. One might say that such a special comment color is what we really want... I agree, and have discussed that elsewhere.  But it is certainly traditional to have program text read monocolor:

     arg1:  111,
     arg2:  222,

Now, you might also argue that keyword arguments subsume the example above.  Sure... but then I can create other examples that are not keyword arguments.

I can imagine comment from beginning of line delimiters other than colon, but none are quite so elegant:

     arg1>>>  111,
     arg2:>>> 222,

     arg1==>  111,
     arg2==> 222,

     arg1:::  111,
     arg2::: 222,

Again, we are limited by the ASCII, or UTF, character set.


Martin said...

VHDL (and I guess ADA) has some of that in that function calls and instantiations can have their arguments mapped in any order, but named:

arg2 => 1,
arg1 => 100,
arg3 => "Hello");

Andy "Krazy" Glew said...

I like keyword arguments, but comments from beginning of line are a separate issue. Similar, since comments often make up for the lack of keyword arguments, but separate, since comments can be used for many other purposes.

Although I suppose that one could say that all human readable names in programs - anything other than register numbers and numeric memory locations - are just comments. Comments that have semantic effect.

Paul A. Clayton said...

One interesting syntax that you did not consider:

comment_content \\ code;

This has a symmetry with C99/C++ "//" comments. Everything in the leaning-to direction from the comment marker until the edge of the line is a comment. One problem with "\\" is that "\" is often used as an escape character and "\\" as a non-escaping "\".

A "code // comment \\ code;" syntax might have been worth considering if "\\" comments were practical.

I do not know if "\\" meets the not "visually heavyweight" requirement. It seems a little visually lighter than "/* */" (not having a preceding mark and the two simple lines kind of elide into a single line), and it would be slightly easier to type (I think--key repeat versus two separate keys--perhaps especially on QWERTY where the "*" requires a shift and the same hand is used for somewhat widely separated keys).